content: package com.yl.countdown;
  
  import android.os.Bundle;
  import android.support.v7.app.AppCompatActivity;
  import android.view.View;
  import android.widget.Button;
  
  import java.util.Timer;
  import java.util.TimerTask;
  
  /**
   * 主页
   * <p>
   * Created by yangle on 2017/12/5.
   * Website：http://www.yangle.tech
   */
  
  public class MainActivity extends AppCompatActivity {
  
      private CountdownView countdownView;
      private Button btnStart;
      private int time = 15;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
          init();
      }
  
      private void init() {
          countdownView = findViewById(R.id.view_countdown);
          btnStart = findViewById(R.id.btn_start);
  
          // 设置倒计时时长
          countdownView.setCountdown(time);
          // 设置倒计时改变监听
          countdownView.setOnCountdownListener(new CountdownView.OnCountdownListener() {
              @Override
              public void countdown(int time) {
                  MainActivity.this.time = time;
              }
          });
  
          // 开始倒计时监听
          btnStart.setOnClickListener(new View.OnClickListener() {
              @Override
              public void onClick(View view) {
                  final Timer timer = new Timer();
                  timer.schedule(new TimerTask() {
                      @Override
                      public void run() {
                          runOnUiThread(new Runnable() {
                              @Override
                              public void run() {
                                  time--;
                                  countdownView.setCountdown(time);
                                  if (time == 0) {
                                      timer.cancel();
                                  }
                              }
                          });
                      }
                  }, 1000, 1000);
              }
          });
      }
  }
  